1. Field of the Invention
The present invention relates to systems for the in-flight refuelling of aircraft.
2. Discussion of Background
In-flight refuelling consists in transferring fuel from a tanker aircraft to a receiver aircraft using a hose which passes through what is commonly known as a boom and a telescopic line extending from this boom. The boom is fixed to the lower rear part of the fuselage of the tanker aircraft by a semi-rigid connection which allows it a certain freedom of movement. The boom and line assembly floats up under the empennage of the tanker aircraft by virtue of ailerons equipped with control surface which allow it to be steered. The total length of the boom and deployed line assembly may be as much as 15 or 20 meters. The receiver aircraft has a receptacle intended to receive the end of the line during refuelling. This receptacle is equipped with locking means for holding the line in place in relation to a pipe which allows the file from the tanker aircraft to be taken into a tank of the receiver aircraft.
The pilot of the receiver aircraft needs to bring his airplane up under the empennage of the tanker aircraft near to the line that extends behind the tanker aircraft, and keep his speed strictly identical to that of the tanker aircraft until the end of the refuelling operation.
The pilot of the receiver aircraft needs to bring his aeroplane up under the empennage of the tanker aircraft near to the line that extends behind the latter, and keep his speed strictly identical to that of the tanker aircraft until the end of the refuelling operation.
There are two ways of connecting the tanks of the tanker aircraft and of the receiver aircraft.
In the first case, the receiver aircraft is equipped with an in-flight refuelling line which extends in the field of view of the pilot, and the hose from the fuel tank of the tanker aircraft extends beyond the boom and the line in the form of a "basket" intended to receive the line of the receiver aircraft. It is therefore the pilot of the receiver aircraft who has to steer his airplane in such a way as to lock his line in the bottom of the basket.
In the second case, to which the present invention is more specifically related, the receiver aircraft is equipped only with a refuelling receptacle, and it is the end of the line from the tanker aircraft which is docked in the receptacle to allow fuel to be transferred. The line is guided by an operator placed in the rear of the tanker aircraft. This operator looks out through a window and performs the operations of coupling the two aircraft so that fuel can be transferred. To do this, the operator has control levers which operate servomotors that steer the boom so that the rear end of the boom/line assembly can be brought up close to the receptacle placed on the receiver aircraft. The position of this receptacle is identified by a painted mark on the aircraft skin. When the line is in the desired position, facing the receptacle, the operator initiates an additional deployment of the end of the telescopic line, and this engages and locks the line in the receptacle. Fuel transfer can then take place. Guiding the line towards the receptacle of the receiver aircraft is a tricky operation because of the relative movements of the two aircraft and of the boom, and because the control surfaces are extremely sensitive at the normal working altitudes and speeds. The operator has to operate the boom controls very gradually, and the time needed to make the connection between the line and the receptacle may be great (i.e., as much as a few minutes), especially if the surrounding air is turbulent.